The purpose of this study is to extend prior research on the effects of endotracheal suctioning (ETS) in newborns by systematically examining two methods of delivering hyperoxygenation breaths and two levels of hyperoxygenation during a controlled ETS procedure on selected physiologic variables. Specific aims are: (1) to compare hyperoxygenation breaths delivered with a manual resuscitation bag (MRB) versus a ventilator on oxygen saturation (Sa)2), intracranial pressure (ICP), heart rate (HR), transcutaneous carbon dioxide (tcCO2), mean airway pressure (Paw) and secretion recovery in a sample of premature infants; (2) to compare hyperoxygenation breaths in which the FIO2 is increased 10% over baseline versus those increased 20% over baseline on SaO2, ICP, HR, tcCO2, Paw and secretion recovery in the same sample of premature infant; (3) to determine if there is a relationship between severity of illness and the ability of a hyperoxygenation delivery method (MRB vs ventilator) and level of hyperoxygenation (10% vs 20% increase in FIO2) to prevent suction induced hypoxemia, bradycardia, hyper/hypocarbia and increased ICP. The sample will consist of 40 intubated and mechanically ventilated premature infants who meet the entrance criteria. Each infant will serve as their own control for 5 controlled ETS procedures' 1 baseline ETS and 4 randomly determined protocols: MRB with a 10% increase in FIO2, MRB with a 20% increase in FIO2. The suctioning interval will be standardized for each infant. Five of the six physiological parameters (SaO2, ICP, HR, tcpO2 and Paw) will be collected simultaneously prior to, during and following the suctioning sequence at 50 samples/second on a calibrated Gould TA 2000 recorder. Secretion recovery will be determined by subtracting the pre- suctioned catheter and mucus trap weights from the post-suction catheter and mucus trap weights. Differences in weights of the suction catheters and mucus traps will be totaled to determine the weight of secretions recovered. Data will be analyzed using within subject repeated measures multiple analysis of variance (RM-MANOVA) and other statistical tests as appropriate. The results of this study will determine the effect of the two methods of delivering hyperoxygenated breaths and two levels of hyperoxygenation and provide data for the establishment of research based ETS protocols in ventilated premature infants.